At present, the majority of medicines widely used as anti-inflammatory agents are non-steroid anti-inflammatory drugs (NSAIDs) that have, as the mechanism of action, an inhibitory action on cyclooxygenase (COX) that is involved in the biosynthesis of prostaglandin E2 (PGE2). However, since PGE2 synthesis activity is present in various tissues in the living body and governs the homeostasis thereof, various side effects are induced when NSAID is administered. For example, PGE2 demonstrates the action of maintaining blood flow in the stomach and kidneys, whereas administration of NSAIDs makes it difficult to maintain local blood flow, thereby causing gastric or renal disorders.
Under such circumstances, the presence of a COX isozyme has been confirmed. In order to distinguish it from the previously identified COX, the conventional type has been named COX-1, while the newly discovered isozyme has been named COX-2. In addition, this COX-2 has been clarified to be induced during inflammation and hardly be expressed at all under normal circumstances. It was also clarified that conventional NSAID are able to non-specifically inhibit both COX-1 and COX-2 enzymes. Therefore, the possibility arose of a compound having COX-2 inhibitory action being useful as a novel anti-inflammatory agent.
There are currently several compounds that are known to selectively inhibit only COX-2 without inhibiting COX-1 (Inflammation and Immunology, 3(1), 29-36, 1995; Bioorganic & Med. Chem. Lett. 5(8), 867-872, 1995, etc.). However, the actions of these compounds are not satisfactory and since some of them do not have an adequate water solubility or oral absorption, there is a need for a drug that demonstrates more effective COX-2 inhibitory action.
In addition, an indole derivative represented by the following formula: (wherein, Ra represents a hydrogen atom, a straight or branched alkyl group having 1 to 7 carbon atoms, a straight or branched alkenyl group having 2 to 7 carbon atoms, a straight or branched alkynyl group having 2 to 7 carbon atoms, a cycloalkenyl group having 4 to 6 carbon atoms, an aryl group, a heteroaryl group, an alkylcarbonyl group in which the alkyl moiety is a straight or branched alkyl group having 1 to 7 carbon atoms, an alkenylcarbonyl group in which the alkenyl moiety is a straight or branched alkenyl group having 2 to 7 carbon atoms, an alkynylcarbonyl group in which the alkynyl moiety is a straight or branched alkynyl group having 2 to 7 carbon atoms, or —(CH2)m—Rd, where m represents an integer of 0 to 3 and Rd represents a cycloalkyl group having 3 to 6 carbon atoms which may be substituted with a straight or branched alkyl group having 1 to 3 carbon atoms; Rb represents —SO2—Re, where Re represents a straight or branched alkyl group having 1 to 3 carbon atoms; and Rc represents an aryl group which may have a substituent, a cycloalkyl group having 3 to 6 carbon atoms which may have a substituent, or a monocyclic heterocyclic group which may have a substituent) that selectively inhibits COX-2 is known from Japanese Patent Application Disclosure Hei No. 10-77266 (Japanese Patent Application Hei No. 9-24567).
The object of the present invention is to provide an indole derivative and a mono- or diazaindole derivative that have COX-2 inhibitory activity and are useful as pharmaceuticals, such as anti-inflammatory agents, etc.
As a result of conducting earnest research for the purpose of developing a compound that selectively or non-selectively inhibits COX-2 and has an anti-inflammatory action comparable to or higher than indometacin and other existing NSAIDs, the inventors of the present application found that a compound represented by the general formula (1) has an excellent anti-inflammatory action and/or improved water solubility, making it useful as a pharmaceutical, thereby leading to completion of the present invention on the basis of this finding.